Wrinkle eliminator



Oct. 10, 1939. R. B'OICEI WRINKLE ELIMiNATOR Filed Dec. 27, 1937 Russell I Boice INVENTOR.

Patented Oct. 10, 1939 UNITED STATES 2,175,337 WRINKLE ELnvnNA'ron Russell Boice, Newburgh, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del a corporation of Delaware Application December 27, 1937, Serial No. 181,743

4 Claims.

This invention relates to a method of embossing sheet material and more particularly to an improved method of embossing continuous pyroxylin coated sheet material.

In producing surface pattern effects on sheet materials by means of embossing, two types of processes are commonly used, namely; those employing roller embossing apparatus and those employing plate embossing apparatus. The present invention relates to the roller type of embossing.

In processes of this type, an engraved steel roller is used with a counter roller for bringing the sheet material in contact therewith. The counter roller is usually made of paper disks on a steel mandrel. Pressure is employed to maintain the rollers in contact and frequently the steel roller with the design engraved thereon is heated, usually by steam. The embossing of pyroxylin coated fabrics is usually carried out under approximately 35 to 50 tons of pressure at the area of contact of the embossing rollers. The steel roller is heated by approximately 90 pounds of steam in the steel roller; The paper counter roller usually carries'the pattern counter to the pattern on the steel roller. The point of contact between the'steel roller and the counter roller is called the nip of the rollers.

In the embossing of coated sheet material, such as pyroxylin coated sheet material, considerable difliculty has hitherto been encountered in that the embossed sheet material immediately after it leaves the nip of the embossing rollers, tends to wrinkle longitudinally. The longitudinal wrinkles remain in the material after it has been wound up in rolls and it has been almost impossible to satisfactorily remove the wrinkles. Various expedients have been proposed to eliminate longitudinal wrinkles thus formed. Some of said expedients involving the use of additional apparatus and treating steps, but none of said expedients have been found .to be satisfactory. For example, one method was to pull the embossed and wrinkled material over the top of a heated embossing roller, with the cloth side against the hot roller and the roller revolving in the opposite direction to the passage of the material. This'method is not satisfactory for the reason that it is necessary to have considerable tension on the material'and when the tension is sufficient to remove the wrinkles, thegrain or embossed design-is pulled out. Other methods such as embossing without tension and embossing with a cold roller have also failed to solve this prob- 55 lem.

This invention has for an object an improved method and apparatus for embossing sheet material which avoids the formation of longitudinal wrinkles in the embossed material. A still further object is a simple and easily operated apparatus for preventing the'formationof longitudinal wrinkles in embossed sheet material. Other objects will appear hereinafter.

The objects of this invention have been accomplished by directing a current or blast of air against the embossed surface of sheet material as it leaves the nip of the embossing rollers. The current of air -is directed against the sheet material by means of .a sparger which is placed adjacent the rollers and which directs the air against the surfaceof the sheet material over substantially its entire width.

In the accompanying drawing, Fig. 1 is a perspective view of roller embossing equipment with means for carrying out the invention.

Fig. 2 .is a diagrammatic sectional elevation taken along line II-II of Fig. 1. 1

Fig. 3 is a perspective view of the air discharging means or sparger.

Fig. 4 shows means for adjustably attaching the sparger to theembossing machine. r

In order that the invention may be more fully understood, a detailed specific example is set forth. This example is merely illustrative and the in"ention is not limited thereto as will be more fully apparent hereinafter.

A'base fabric, shown as I in the drawing such as a woven cotton sheeting running 6.4 yards per pound of 40 in. width material (weighing 2.5 ounces per yard per 40" width) and having a thread count of 48 x 48 was given three coats of the following composition, conventional knife coating equipment (not shown) being used:

Per cent Cellulose nitrate 14.0

Pigment; 21.0 Castor oil l7. 5 Ethyl acetate r. 19.0 Ethyl alcohol 28.5

the volatile solvents were evaporated, the dry film consisted of:

The dry strip 1 of the material thus prepared was placed on unwind roller 2 (see Fig. 2) of the apparatus shown in Figs. 1 and 2. The pyroxylin coated sheet material i was passed upwardly to paper counter roller 4, and then between engraved steel roller 3 and the paper counter roller 4, and thence downwardly from roller 4 and under guide roller 5 to windup roller I, all as shown in Fig. 2. The engraved steel roller 3 was heated to a surface temperature of approximately 280 F. The pressure between the steel roller and the counter roller was about 40 tons. A blast of com ressed air was discharged from sparger 1 upon the pyroxylin coated, surface of the sheet material as it left the nip of the embossing rollers I and l.

The sparger I had a series of orifices 8 (Fig. 3) in its discharge face 9, so arranged as to direct the air blast against the embossed surface of the sheet material over substantially the entire width. The discharge face 9 was V inch wide. The orifices 8 were Y; inch in diameter and spaced 1 inch apart in a straight line in the discharge face 9 of the sparger 1. The total area of all the orifices 8 was less than the cross section area of the supply'line III, which was connected to one end of the sparger. The supply line l0 included pressure gauge II and valve I: by means of which the force of the air blast was controlled. The sparger I was attached to the machine frame I! through vertical adjustment ll, horizontal adjustment I5 and angular adjustment It, all as shown in detail in Fig. 4. By means of these adjustments, the discharge face 9 of the sparger 1 was set at approximately 2 inches from the nip of the embossing rollers in such manner that the air blast struck the embossed pyroxylin coated surface of the sheet material approximately one inch from the nip. The air pressure was set at a point between 15 and 30 lbs. per sq; inch as measured by gauge Ii and this air blast forced the embossed sheet material against counter roller 4 in an unwrinkled condition.

A strip of the same sheet material as above disclosed was embossed in the conventional prior art method, using a prior art roller embossing apparatus which did not embody the hereindisclosed invention. The sheet material thus embossed wrinkled badly upon leaving the embossing rollers and a high percentage of the material was unmarketable because of such wrinkling. v

- In general sheetings and drills coated with pyroxylin compositions having a low oil content have a greater tendency to wrinkle than have some other fabrics, and the invention is especia1-. ly valuable for embossing such materials.

While the invention has been specifically described with reference to a particular material, the invention is suitable for embossing other types of sheet material, coated or uncoated, such, for example, as paper, sheets of cellulose derivatives or regenerated cellulose and other fabrics.

Suitable changes may be made in the apparatus without departing from the spirit of the invention. Thus, while a hot steel roller-has been dis-- closed in the specific example, the embossing may I be done with a cold steel roller. Pyroxylin coating is heat moldable and a better grain results with a heated roller than a cold roller. For this reason, hot embossing rollers are almost universally used in the pyroxylin coated fabric industry and hot embossing is preferred in the present invention.

The particular shape of the sparger shown in Fig. 3 is preferred because it permits the discharge face 0 of the sparger to be brought in close proximity of the embossing rollers. Other suitable shapes may, however, be used. In the preferred embodiment of the invention, the air is discharged throushaseriesof orifices as has been described, but the number and size of the orifices may be varied as desired. Other types of orifices may be used, as for example, a series of longitudinal slits or a single narrow longitudinal slit running the length of the sparger. Regardless of the type of discharge orifice used, the relation of the size of the air inlet to the total area of the discharge orifices should be such as to insure a fairly uniform pressure through the entire length of the sparger. While the specific example has shown a single inlet located at one end of the sparger, the inlet may be located at the center of the sparger, or several inlets may be used as, for example, one at each end of the sparger.

It is very important that the air blast strike the embossed sheet material before longitudinal wrinkles are formed. After the wrinkles are once formed, the air blast does not remove them. The

prevention of wrinkles has been accomplished by directing the air blast so as to impinge upon the embossed sheet not more than 1% inches away from the nip of the embossing rollers. If'the air blast impinges upon the embossed sheet at a greater distance from the nip, longitudinal wrinkles will form therein. In order to obtain the best results, the discharge face 5 of the sparger should not be further than 2 inches from the nip of the embossing rollers and the force of the air blast should be directed against the embossed surface of the sheet material approximately one inch from the nip of the embossing rollers. Forvarioustypesofpyroxylincoatedsheet material, including pyroxylin coated papers, the minimum effective air pressure varies under the above conditions and in ,the materials treated so far from 5 to 55 lbs. per sq. inch, as determined by gauge ll. Higher air pressures may be used but there is no particular advantage in a pressure greater than the minimum amount required to prevent longitudinal wrinkles. While the above conditions are preferred other conditions may be used if desired; for example, with high pressures the sparger may be located farther away from the nip of the rollers.

For special purposes, the compressed air discharged from sparger 'I may be heated. Preferably the air is at or below room temperature. Since the heat of the engraved steel roller deteriorates the paper counter roller, the cooling effect of the air blast tends to increase the life of the paper counter roller.

While the invention is not limited to any theory, the following is believed to be an explanation of the reason that it produces the improvement herein set forth. Before the embossing operation of coated fabric, the material is, smooth.

- The embossing operation contorts the material and sets up transverse components of force which "cause'the material to creep transversely which in conventional manufacturing processes results in the bulging or bellying" of the embossed sheet. The force of the air which is discharged on the surface of the embossed sheet immediately after it leaves the nip of the engraved steel roller and paper counter roller is greater than the transverse components of force which wrinkles the smooth material. The force of the' compressed air striking the embossed surface prevents bellying and keeps the entire sheet in direct contact with the paper roller at the point where the air strikes the embossed sheet for a very short interval of time which is sufllcient to prevent longitudinal wrinkling of the embossed material.

The process and apparatus disclosed above have been found to be completely effective in the prevention of the formation of longitudinal wrinkles I in pyroxylin coated fabrics during the embossing operation. Prior art expedients for preventing and removing wrinkles have been expensive both in original cost and maintenance. Moreover, these frequently added another operation to the manufacture of coated sheet material. In contrast therewith, the present invention may be carried out at low initial and low maintenance cost. The present invention does not increase the time necessary to carry out the embossing process nor does it require equipment which will take up floor space. A still further advantage of the present invention is that while it effectively prevents the formation of wrinkles, it does not in any way affect the grain which has been embossed upon the sheet material.

Suitable changes may be made in the details of the process and the apparatus and any modifications or variations which conform to the spirit of the invention are intended to be included within the scope of the claims.

It is apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof; and, therefore, it is not intended to be limited except as indicated in the appended claims.

I claim: g

1. Embossing process which comprises pa'ssing' pyroxylin coated sheet material upwardly to a counter roller, over the counter roller and downwardly away from the counter roller, embossing the sheet material with an engraved roller while the sheet material is in contact with the counter roller and directing a current of air upon substantially the entire width of the embossed pyroxylin coated surface of the sheet material within 1 inches of the nip of the rollers, whereby the embossed sheet material is forced in contact with the counter roller.

2. In the process of embossing long lengths of fabrics coated with a substantially dry film of a cellulose derivative composition wherein the fabric is passed between a metallic embossing roller and a registering counter roller, and wherein longitudinal wrinkles are normally produced as the coated fabric emerges from the said rollers, the improvement of preventing the formation of the longitudinal wrinkles which comprises the step of directing a blast of air against the fabric as it emerges from between the embossing roll and the counter roll, said blast of air being directed-in a direction substantially perpendicular to the line of contact between the said rollers and within two inches thereof.

3. The process of embossing fabrics having a dry coating of a cellulose derivative composition which comprises passing the coated fabric between a metallic roller having a design engraved thereon and a counter roller having the said design impressed therein and directing a blast of air against the fabric as it emerges from between the said rollers, said blast of air being directed in a direction substantially perpendicular to the line of contact between the said rollers and within two inches thereof.

4. An apparatus for embossing webs of fabrics coated with a dry pyroxylin composition comprising an engraved roller. a counter roller having a surface which registers with the engraving on the engraved roller and which is in contact therewith, a sparger positioned within about two inches from the line of contact between the said engraved and counter rollers on the side of the line of contact from which the embossed web emerges, and means for passing air through the sparger against the line of contact between the said rollers in a direction substantially perpendicular to the line of contact between the said rollers.

RUSSELL BOICE. 

